Mack U Series Problems by year

Steering wheel retaining nuts may have been improperly installed and/or torqued.

An incorrect high pressure power steering hose may have been installed.

Some of the nuts/bolts used to fasten the steering pitman arm may loosen.

Clamp plates used between the drive shaft and carrier yokes may crack and could break due to improper heat treatment.

Cross steering levers may be improperly heat treated and subject to fail during normal operation.

Improper steering clamp bolts and torque applied during installation. The bolt could fail, allowing the steering yoke to become loose.

Certain vehicles may be subject to steering shaft separation due to loose set screws in the dash sheet bearing which may allow the shaft to move.

The retaining pin for the brake control knob has been misaligned (off the center line of the valve plunger hole). This causes the knob to be overstressed at the retaining pin hole area causing it to separate from the valve.

The prefabricated pinch bolt clamp at the lower steering shaft lower yoke may not perform adequately when tightened to specifications. The clamp may then deform and loss of clamping force and steering shaft disengagement may result.

On certain vehicles, the knob that operates the tractor park valve may break off, rendering the valve inoperable.